// Ported from Stefan Gustavson's java implementation
// http://staffwww.itn.liu.se/~stegu/simplexnoise/simplexnoise.pdf
// Read Stefan's excellent paper for details on how this code works.
//
// Sean McCullough banksean@gmail.com
//
// Added 4D noise

/**
 * You can pass in a random number generator object if you like.
 * It is assumed to have a random() method.
 */
class SimplexNoise {
  constructor(r = Math) {
    this.grad3 = [
      [1, 1, 0],
      [-1, 1, 0],
      [1, -1, 0],
      [-1, -1, 0],
      [1, 0, 1],
      [-1, 0, 1],
      [1, 0, -1],
      [-1, 0, -1],
      [0, 1, 1],
      [0, -1, 1],
      [0, 1, -1],
      [0, -1, -1],
    ];
    this.grad4 = [
      [0, 1, 1, 1],
      [0, 1, 1, -1],
      [0, 1, -1, 1],
      [0, 1, -1, -1],
      [0, -1, 1, 1],
      [0, -1, 1, -1],
      [0, -1, -1, 1],
      [0, -1, -1, -1],
      [1, 0, 1, 1],
      [1, 0, 1, -1],
      [1, 0, -1, 1],
      [1, 0, -1, -1],
      [-1, 0, 1, 1],
      [-1, 0, 1, -1],
      [-1, 0, -1, 1],
      [-1, 0, -1, -1],
      [1, 1, 0, 1],
      [1, 1, 0, -1],
      [1, -1, 0, 1],
      [1, -1, 0, -1],
      [-1, 1, 0, 1],
      [-1, 1, 0, -1],
      [-1, -1, 0, 1],
      [-1, -1, 0, -1],
      [1, 1, 1, 0],
      [1, 1, -1, 0],
      [1, -1, 1, 0],
      [1, -1, -1, 0],
      [-1, 1, 1, 0],
      [-1, 1, -1, 0],
      [-1, -1, 1, 0],
      [-1, -1, -1, 0],
    ];
    this.p = [];
    for (let i = 0; i < 256; i++) {
      this.p[i] = Math.floor(r.random() * 256);
    }

    // To remove the need for index wrapping, double the permutation table length
    this.perm = [];
    for (let i = 0; i < 512; i++) {
      this.perm[i] = this.p[i & 255];
    }

    // A lookup table to traverse the simplex around a given point in 4D.
    // Details can be found where this table is used, in the 4D noise method.
    this.simplex = [
      [0, 1, 2, 3],
      [0, 1, 3, 2],
      [0, 0, 0, 0],
      [0, 2, 3, 1],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [1, 2, 3, 0],
      [0, 2, 1, 3],
      [0, 0, 0, 0],
      [0, 3, 1, 2],
      [0, 3, 2, 1],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [1, 3, 2, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [1, 2, 0, 3],
      [0, 0, 0, 0],
      [1, 3, 0, 2],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [2, 3, 0, 1],
      [2, 3, 1, 0],
      [1, 0, 2, 3],
      [1, 0, 3, 2],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [2, 0, 3, 1],
      [0, 0, 0, 0],
      [2, 1, 3, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [2, 0, 1, 3],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [3, 0, 1, 2],
      [3, 0, 2, 1],
      [0, 0, 0, 0],
      [3, 1, 2, 0],
      [2, 1, 0, 3],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [0, 0, 0, 0],
      [3, 1, 0, 2],
      [0, 0, 0, 0],
      [3, 2, 0, 1],
      [3, 2, 1, 0],
    ];
  }
  dot(g, x, y) {
    return g[0] * x + g[1] * y;
  }
  dot3(g, x, y, z) {
    return g[0] * x + g[1] * y + g[2] * z;
  }
  dot4(g, x, y, z, w) {
    return g[0] * x + g[1] * y + g[2] * z + g[3] * w;
  }
  noise(xin, yin) {
    let n0; // Noise contributions from the three corners
    let n1;
    let n2;
    // Skew the input space to determine which simplex cell we're in
    const F2 = 0.5 * (Math.sqrt(3.0) - 1.0);
    const s = (xin + yin) * F2; // Hairy factor for 2D
    const i = Math.floor(xin + s);
    const j = Math.floor(yin + s);
    const G2 = (3.0 - Math.sqrt(3.0)) / 6.0;
    const t = (i + j) * G2;
    const X0 = i - t; // Unskew the cell origin back to (x,y) space
    const Y0 = j - t;
    const x0 = xin - X0; // The x,y distances from the cell origin
    const y0 = yin - Y0;

    // For the 2D case, the simplex shape is an equilateral triangle.
    // Determine which simplex we are in.
    let i1; // Offsets for second (middle) corner of simplex in (i,j) coords

    let j1;
    if (x0 > y0) {
      i1 = 1;
      j1 = 0;

      // lower triangle, XY order: (0,0)->(1,0)->(1,1)
    } else {
      i1 = 0;
      j1 = 1;
    } // upper triangle, YX order: (0,0)->(0,1)->(1,1)

    // A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and
    // a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where
    // c = (3-sqrt(3))/6
    const x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords
    const y1 = y0 - j1 + G2;
    const x2 = x0 - 1.0 + 2.0 * G2; // Offsets for last corner in (x,y) unskewed coords
    const y2 = y0 - 1.0 + 2.0 * G2;
    // Work out the hashed gradient indices of the three simplex corners
    const ii = i & 255;
    const jj = j & 255;
    const gi0 = this.perm[ii + this.perm[jj]] % 12;
    const gi1 = this.perm[ii + i1 + this.perm[jj + j1]] % 12;
    const gi2 = this.perm[ii + 1 + this.perm[jj + 1]] % 12;
    // Calculate the contribution from the three corners
    let t0 = 0.5 - x0 * x0 - y0 * y0;
    if (t0 < 0) n0 = 0.0;
    else {
      t0 *= t0;
      n0 = t0 * t0 * this.dot(this.grad3[gi0], x0, y0); // (x,y) of grad3 used for 2D gradient
    }

    let t1 = 0.5 - x1 * x1 - y1 * y1;
    if (t1 < 0) n1 = 0.0;
    else {
      t1 *= t1;
      n1 = t1 * t1 * this.dot(this.grad3[gi1], x1, y1);
    }

    let t2 = 0.5 - x2 * x2 - y2 * y2;
    if (t2 < 0) n2 = 0.0;
    else {
      t2 *= t2;
      n2 = t2 * t2 * this.dot(this.grad3[gi2], x2, y2);
    }

    // Add contributions from each corner to get the final noise value.
    // The result is scaled to return values in the interval [-1,1].
    return 70.0 * (n0 + n1 + n2);
  }

  // 3D simplex noise
  noise3d(xin, yin, zin) {
    let n0; // Noise contributions from the four corners
    let n1;
    let n2;
    let n3;
    // Skew the input space to determine which simplex cell we're in
    const F3 = 1.0 / 3.0;
    const s = (xin + yin + zin) * F3; // Very nice and simple skew factor for 3D
    const i = Math.floor(xin + s);
    const j = Math.floor(yin + s);
    const k = Math.floor(zin + s);
    const G3 = 1.0 / 6.0; // Very nice and simple unskew factor, too
    const t = (i + j + k) * G3;
    const X0 = i - t; // Unskew the cell origin back to (x,y,z) space
    const Y0 = j - t;
    const Z0 = k - t;
    const x0 = xin - X0; // The x,y,z distances from the cell origin
    const y0 = yin - Y0;
    const z0 = zin - Z0;

    // For the 3D case, the simplex shape is a slightly irregular tetrahedron.
    // Determine which simplex we are in.
    let i1; // Offsets for second corner of simplex in (i,j,k) coords

    let j1;
    let k1;
    let i2; // Offsets for third corner of simplex in (i,j,k) coords
    let j2;
    let k2;
    if (x0 >= y0) {
      if (y0 >= z0) {
        i1 = 1;
        j1 = 0;
        k1 = 0;
        i2 = 1;
        j2 = 1;
        k2 = 0;

        // X Y Z order
      } else if (x0 >= z0) {
        i1 = 1;
        j1 = 0;
        k1 = 0;
        i2 = 1;
        j2 = 0;
        k2 = 1;

        // X Z Y order
      } else {
        i1 = 0;
        j1 = 0;
        k1 = 1;
        i2 = 1;
        j2 = 0;
        k2 = 1;
      } // Z X Y order
    } else {
      // x0<y0

      if (y0 < z0) {
        i1 = 0;
        j1 = 0;
        k1 = 1;
        i2 = 0;
        j2 = 1;
        k2 = 1;

        // Z Y X order
      } else if (x0 < z0) {
        i1 = 0;
        j1 = 1;
        k1 = 0;
        i2 = 0;
        j2 = 1;
        k2 = 1;

        // Y Z X order
      } else {
        i1 = 0;
        j1 = 1;
        k1 = 0;
        i2 = 1;
        j2 = 1;
        k2 = 0;
      } // Y X Z order
    }

    // A step of (1,0,0) in (i,j,k) means a step of (1-c,-c,-c) in (x,y,z),
    // a step of (0,1,0) in (i,j,k) means a step of (-c,1-c,-c) in (x,y,z), and
    // a step of (0,0,1) in (i,j,k) means a step of (-c,-c,1-c) in (x,y,z), where
    // c = 1/6.
    const x1 = x0 - i1 + G3; // Offsets for second corner in (x,y,z) coords
    const y1 = y0 - j1 + G3;
    const z1 = z0 - k1 + G3;
    const x2 = x0 - i2 + 2.0 * G3; // Offsets for third corner in (x,y,z) coords
    const y2 = y0 - j2 + 2.0 * G3;
    const z2 = z0 - k2 + 2.0 * G3;
    const x3 = x0 - 1.0 + 3.0 * G3; // Offsets for last corner in (x,y,z) coords
    const y3 = y0 - 1.0 + 3.0 * G3;
    const z3 = z0 - 1.0 + 3.0 * G3;
    // Work out the hashed gradient indices of the four simplex corners
    const ii = i & 255;
    const jj = j & 255;
    const kk = k & 255;
    const gi0 = this.perm[ii + this.perm[jj + this.perm[kk]]] % 12;
    const gi1 =
      this.perm[ii + i1 + this.perm[jj + j1 + this.perm[kk + k1]]] % 12;
    const gi2 =
      this.perm[ii + i2 + this.perm[jj + j2 + this.perm[kk + k2]]] % 12;
    const gi3 = this.perm[ii + 1 + this.perm[jj + 1 + this.perm[kk + 1]]] % 12;
    // Calculate the contribution from the four corners
    let t0 = 0.6 - x0 * x0 - y0 * y0 - z0 * z0;
    if (t0 < 0) n0 = 0.0;
    else {
      t0 *= t0;
      n0 = t0 * t0 * this.dot3(this.grad3[gi0], x0, y0, z0);
    }

    let t1 = 0.6 - x1 * x1 - y1 * y1 - z1 * z1;
    if (t1 < 0) n1 = 0.0;
    else {
      t1 *= t1;
      n1 = t1 * t1 * this.dot3(this.grad3[gi1], x1, y1, z1);
    }

    let t2 = 0.6 - x2 * x2 - y2 * y2 - z2 * z2;
    if (t2 < 0) n2 = 0.0;
    else {
      t2 *= t2;
      n2 = t2 * t2 * this.dot3(this.grad3[gi2], x2, y2, z2);
    }

    let t3 = 0.6 - x3 * x3 - y3 * y3 - z3 * z3;
    if (t3 < 0) n3 = 0.0;
    else {
      t3 *= t3;
      n3 = t3 * t3 * this.dot3(this.grad3[gi3], x3, y3, z3);
    }

    // Add contributions from each corner to get the final noise value.
    // The result is scaled to stay just inside [-1,1]
    return 32.0 * (n0 + n1 + n2 + n3);
  }

  // 4D simplex noise
  noise4d(x, y, z, w) {
    // For faster and easier lookups
    const grad4 = this.grad4;
    const simplex = this.simplex;
    const perm = this.perm;

    // The skewing and unskewing factors are hairy again for the 4D case
    const F4 = (Math.sqrt(5.0) - 1.0) / 4.0;
    const G4 = (5.0 - Math.sqrt(5.0)) / 20.0;
    let n0; // Noise contributions from the five corners
    let n1;
    let n2;
    let n3;
    let n4;
    // Skew the (x,y,z,w) space to determine which cell of 24 simplices we're in
    const s = (x + y + z + w) * F4; // Factor for 4D skewing
    const i = Math.floor(x + s);
    const j = Math.floor(y + s);
    const k = Math.floor(z + s);
    const l = Math.floor(w + s);
    const t = (i + j + k + l) * G4; // Factor for 4D unskewing
    const X0 = i - t; // Unskew the cell origin back to (x,y,z,w) space
    const Y0 = j - t;
    const Z0 = k - t;
    const W0 = l - t;
    const x0 = x - X0; // The x,y,z,w distances from the cell origin
    const y0 = y - Y0;
    const z0 = z - Z0;
    const w0 = w - W0;

    // For the 4D case, the simplex is a 4D shape I won't even try to describe.
    // To find out which of the 24 possible simplices we're in, we need to
    // determine the magnitude ordering of x0, y0, z0 and w0.
    // The method below is a good way of finding the ordering of x,y,z,w and
    // then find the correct traversal order for the simplex we’re in.
    // First, six pair-wise comparisons are performed between each possible pair
    // of the four coordinates, and the results are used to add up binary bits
    // for an integer index.
    const c1 = x0 > y0 ? 32 : 0;
    const c2 = x0 > z0 ? 16 : 0;
    const c3 = y0 > z0 ? 8 : 0;
    const c4 = x0 > w0 ? 4 : 0;
    const c5 = y0 > w0 ? 2 : 0;
    const c6 = z0 > w0 ? 1 : 0;
    const c = c1 + c2 + c3 + c4 + c5 + c6;

    // simplex[c] is a 4-vector with the numbers 0, 1, 2 and 3 in some order.
    // Many values of c will never occur, since e.g. x>y>z>w makes x<z, y<w and x<w
    // impossible. Only the 24 indices which have non-zero entries make any sense.
    // We use a thresholding to set the coordinates in turn from the largest magnitude.
    // The number 3 in the "simplex" array is at the position of the largest coordinate.
    const i1 = simplex[c][0] >= 3 ? 1 : 0;
    const j1 = simplex[c][1] >= 3 ? 1 : 0;
    const k1 = simplex[c][2] >= 3 ? 1 : 0;
    const l1 = simplex[c][3] >= 3 ? 1 : 0;
    // The number 2 in the "simplex" array is at the second largest coordinate.
    const i2 = simplex[c][0] >= 2 ? 1 : 0;
    const j2 = simplex[c][1] >= 2 ? 1 : 0;
    const k2 = simplex[c][2] >= 2 ? 1 : 0;
    const l2 = simplex[c][3] >= 2 ? 1 : 0;
    // The number 1 in the "simplex" array is at the second smallest coordinate.
    const i3 = simplex[c][0] >= 1 ? 1 : 0;
    const j3 = simplex[c][1] >= 1 ? 1 : 0;
    const k3 = simplex[c][2] >= 1 ? 1 : 0;
    const l3 = simplex[c][3] >= 1 ? 1 : 0;
    // The fifth corner has all coordinate offsets = 1, so no need to look that up.
    const x1 = x0 - i1 + G4; // Offsets for second corner in (x,y,z,w) coords
    const y1 = y0 - j1 + G4;
    const z1 = z0 - k1 + G4;
    const w1 = w0 - l1 + G4;
    const x2 = x0 - i2 + 2.0 * G4; // Offsets for third corner in (x,y,z,w) coords
    const y2 = y0 - j2 + 2.0 * G4;
    const z2 = z0 - k2 + 2.0 * G4;
    const w2 = w0 - l2 + 2.0 * G4;
    const x3 = x0 - i3 + 3.0 * G4; // Offsets for fourth corner in (x,y,z,w) coords
    const y3 = y0 - j3 + 3.0 * G4;
    const z3 = z0 - k3 + 3.0 * G4;
    const w3 = w0 - l3 + 3.0 * G4;
    const x4 = x0 - 1.0 + 4.0 * G4; // Offsets for last corner in (x,y,z,w) coords
    const y4 = y0 - 1.0 + 4.0 * G4;
    const z4 = z0 - 1.0 + 4.0 * G4;
    const w4 = w0 - 1.0 + 4.0 * G4;
    // Work out the hashed gradient indices of the five simplex corners
    const ii = i & 255;
    const jj = j & 255;
    const kk = k & 255;
    const ll = l & 255;
    const gi0 = perm[ii + perm[jj + perm[kk + perm[ll]]]] % 32;
    const gi1 =
      perm[ii + i1 + perm[jj + j1 + perm[kk + k1 + perm[ll + l1]]]] % 32;
    const gi2 =
      perm[ii + i2 + perm[jj + j2 + perm[kk + k2 + perm[ll + l2]]]] % 32;
    const gi3 =
      perm[ii + i3 + perm[jj + j3 + perm[kk + k3 + perm[ll + l3]]]] % 32;
    const gi4 = perm[ii + 1 + perm[jj + 1 + perm[kk + 1 + perm[ll + 1]]]] % 32;
    // Calculate the contribution from the five corners
    let t0 = 0.6 - x0 * x0 - y0 * y0 - z0 * z0 - w0 * w0;
    if (t0 < 0) n0 = 0.0;
    else {
      t0 *= t0;
      n0 = t0 * t0 * this.dot4(grad4[gi0], x0, y0, z0, w0);
    }

    let t1 = 0.6 - x1 * x1 - y1 * y1 - z1 * z1 - w1 * w1;
    if (t1 < 0) n1 = 0.0;
    else {
      t1 *= t1;
      n1 = t1 * t1 * this.dot4(grad4[gi1], x1, y1, z1, w1);
    }

    let t2 = 0.6 - x2 * x2 - y2 * y2 - z2 * z2 - w2 * w2;
    if (t2 < 0) n2 = 0.0;
    else {
      t2 *= t2;
      n2 = t2 * t2 * this.dot4(grad4[gi2], x2, y2, z2, w2);
    }

    let t3 = 0.6 - x3 * x3 - y3 * y3 - z3 * z3 - w3 * w3;
    if (t3 < 0) n3 = 0.0;
    else {
      t3 *= t3;
      n3 = t3 * t3 * this.dot4(grad4[gi3], x3, y3, z3, w3);
    }

    let t4 = 0.6 - x4 * x4 - y4 * y4 - z4 * z4 - w4 * w4;
    if (t4 < 0) n4 = 0.0;
    else {
      t4 *= t4;
      n4 = t4 * t4 * this.dot4(grad4[gi4], x4, y4, z4, w4);
    }

    // Sum up and scale the result to cover the range [-1,1]
    return 27.0 * (n0 + n1 + n2 + n3 + n4);
  }
}

export { SimplexNoise };
